Electronic pulsing device



April 15, 1958 F. A. OBLOY ELECTRONIC PUL'SING DEVICE Filed March 16.1956 hDmhDO INVENTOR FELIX A. OBLOY ATTORNEY United States PatentELECTRONIC PULSIN G DEVICE Felix A. Obloy, Rancho Santa Fe, Calif,assignor to Bill Jack Scientific Instrument Co., Solana Beach, Calif., acorporation of California Application March 16, 1956, Serial No. 572,088

14 Claims. (Cl. 307-132) One object of my invention is to provide apulsing device or pulse switch generator having a high degree ofstability.

Another object is the provision of a pulse switch generator whose switchrepetition rate is substantially constant under wide variations ofambient temperature and power source conditions.

An additional object of this invention is to produce apulse switchingdevice wherein the switching time interval and repetition rate remainconstant under a substantial range of temperature and input voltagevariations.

More specifically, it is an object of the present invention to provide aprecision timer or switching device utilizing a pulse shaping and timinggenerator having a gaseous electronic discharge device in combinationwith temperature and current responsive devices in a novel circuit.

In particular it is an object of my invention to devise a gas tetrodeelectronic switching device of precision stability having bothtemperature-responsive and currentresponsive resistance means.

With the foregoing and other objects in view the invention resides inthe combination of parts and in the details of construction set forth inthe following specification and appended claims, certain embodiments ofwhich are illustrated in the drawing which is a circuit diagramincluding the details of a preferred embodiment of the electronic pulseswitch devicein accordance with my invention.

Considering the figure in detail, the circuitof the switching device maybe conveniently assembled in a plug-in package as is well knownin theart and may be provided with external contacts indicated at terminalblock T. As indicated by the drawing legends, contacts AB are to beconnected to an alternating current power source of 115 volts nominalpotential at a frequency of 50 to 1000 cycles; contacts CD may beconnected to an external initiating switch SW; and the times pulseswitching output may be taken oil at contacts EF.

The input voltage from contacts AB is applied to primary winding 29 oftransformer through switch 37. This is shown schematically as a.voltage. of magnitude E supplied by the generator 36 indicated in dottedoutline. The cathode heater 13, 14 of gas tetrode 21 is energized fromterminals 11, 12 of secondary winding 38 of transformer 10, whichwinding is center-tapped to ground at 35 as indicated. Anode potentialis applied at plate 21 of the tetrode 21 through a current limitingresistor 12 from transformer secondary winding 30. Secondary 3G isoptionally a step-up winding which raises the applied anode potentialapproximately 20 precent above the input source E to insure positiveaction of the circuit of load relay 28 which controls the timedswitching cycle.

Load relay 28 is a double-pole double-throw type whose contacts areshown in unenergized position. This relay is connected in the cathodecircuit of tetrode 21 through a path which may be traced from the tubecathode through 2,831,130 Patented Apr. is, 1958 terminal contacts CDwhen bridged by the time cycle initiating switch SW, thence throughresistor 23 to the positive lead of relay 28, with the circuit completedthrough the relay winding and resistors T25, T26 to ground.

The grid circuit of the gas tetrode switching device ineludestemperature compensating resistors 20 and 15. Resistor 20 has a negativeresistance coefficient, while resistor 15 has positive resistancecoeflicient, to efifect calibration accuracy despite ambient temperaturechanges. One end of resistor 20 is connected to load relay terminal 33which is cyclically grounded at contact 31 during operation of thedevice, while the opposite end of this resistor connects to the tetrodegrid through grid limiting resistor 18. The grid is returned to thecathode through a resistance capacitance voltage divider network made upof calibration potentiometer 16, condenser 17, and temperaturecompensating resistor 15.

The resistance capacitance combination of condenser 22 and variableresistor 23 controls the pulse duration or pulse cycle for the grid biasof tube 21, which effectually determines the cyclic switching rate atoutput terminal contacts EF, as will be more fully explained hereinafterwhen the operation of the complete circuit of the invention isdescribed. One end of condenser 22 is directly connected to the tetrodegrid, and the opposite end thereof connects to resistor 23 as shown.

It will now be noted that the winding of load relay 28 is shunted by aparallel combination of condenser 27 andresistor T24, and the lower endof such winding is grounded through resistors T25, T26 which areconnected in parallel. Resistors T24, T25 and T26 are of the type whichdemonstrate a non-linear resistance characteristic with respect toapplied current, and may be of the variety generally designated asVaristors which may be compounded with thyrites or other known media toeflect such non-linear characteristics.

The non-linear resistance elements are utilized as a means ofcompensating for current variations and thus serve to stabilize thepulsing cycle of the circuit within voltage differentials ofplus-and-minus-15 percent from the normal volt input valve. Thiscompensation effect has been found to be an essential factor in attain-ving a highly precise switch timing cycle according to my invention.Timing intervals of precision accuracy may be maintained under severevariations of input potential values for either sustained or varyingconditions ofundervoltage or over-voltage.

As previously mentioned, the pulse width duration of the outputswitching cycle is basically determined by the values of condenser 22and resistor 23. However, it is to be noted that this pulse width valuemay be influenced by the resistance capacitance time constant ofthe-parallel combination of the winding of load relay 28 and condenser27. The varistor T24 which is shunted across this latter combinationstabilizes the effect of induced potential surges created due to theinductive action of the relay winding when the current therethroughcollapses, and thus prevents any undesired timing cycle variations.

The manner in which this invention operates to provide a precision timedpulse switching rate may be explained as follows. With switch 37 closed,the external initiating contacts of switch SW connected across contactsCD, and an adequate alternating current potential source applied at AB,within approximately ten seconds load relay 28 will be energized due tocurrent flow through tetrode 21. This current flow will have taken placedue to the fact that the tube cathode has been raised up to emittingtemperature by the heater voltage from secondary 38, while at the sametime recurrent positive swings 3 of potential have been applied to thetetrode plate 21' by transformer winding 30, until a gas discharge orconduction between the plate 21 and the cathode occurs. Also during thisperiod the tetrode control grid 21A has built up a high negative biasingvoltage across condenser 17.

When load relay 28 is energized, contacts 31 and 33 are closed whichprovides a momentary negative grid bias potential on control grid 21Athrough grid resistor 18. Since the plate 21' of tetrode 21 is energizedfrom an alternating current source, plate current flow will stop withinone half-cycle of applied plate voltage when the grid has attained abias value below cutoit.

When load relay 28 is energized the output contacts 32, 34 provide anisolated switching pulse at contact terminals EF. As shown in thefigure, this switch pulse will be a circuit closing pulse. if a circuitopening pulse is required, the contact E may be connected to relaycontact 40 rather than to contact 34. Relay 28 and the contacts thereofmay be shielded if necessary, as indicated in dotted outline at 3?.

When plate current flow ceases relay 2?; opens, the high negative "ridbias dissipates from condenser 17, and the tetrode Zll will remaindeionized and non-conducting until condenser 17 discharges to a valuesufiicient to permit plate current flow to be reiuitiated. Thus,repetitive switch cycling action is obtained.

it should be noted that resistors 1.5 and T26 are' parallel connected. Ihave found experimentally that this is a preferable expedient whicheilfects a high degree of stable operation despite variations in appliedinput voltage. Greater stability is achieved with this parallelconnection than by the use of a single varistor of equivalent resistancevalue. I believe that this may be explained as being due to acompensating action within the resistors, whereby non-uniform currentvs. resistance characteristics are cancelled out or otherwisecompensated.

It will be apparent to those skilled in the art that various changes maybe made in the circuitry from that of the preferred embodiment which Ihave shown in the drawing, and that further uses for such a pulsingdevice may be contemplated. For example, the invention may be used incascade multiple circuit switching operations by the simple expedient ofproviding a plurality of such devices in a series chain. Thus the outputswitch pulse from contacts EF of a first unit could be connected to theinitiating contacts CD of a second unit, and so on. Accordingly, thescope of the invention is to be construe-d as indicated in the appendedclaims.

I claim:

1. A pulse timing generator including an electron current switchingdevice and temperature responsive stabilizing means therefor.

2. A pulse timing generator including an electron current switchingdevice and current responsive stabilizing means therefor.

3. A pulse timing generator including an electron current switchingdevice, first means to stabilize said device for temperature variations,and second means to stabilize said device for current variations.

4. A stabilized pulse switch generator including, in combination, anelectron discharge device, first circuit means to apply operatingpotentials to said device, second circuit means cyclically energized bysaid device, and stabilizing means associated with at least one of saidcircuit means.

5. A Stabilized pulse switch generator according to claim 4 in whichsaid stabilizing means is temperature responsive.

6. A stabilized pulse switch generator according to claim 4 in whichsaid stabilizing means is current responsrve.

7. A stabilized pulse switch generator according to claim 4 in whichsaid last-named means stabilizes for both temperature and currentvariations.

A pulsing device for determining recurrent timing intervals includingelectron discharge means having at least an input circuit and an outputcircuit, a source of potential, connections between said source and saiddischarge means such that current fiow is established in each circuitfor at least a portion of such recurrent intervals, and temperatureresponsive means to regulate said current flow.

9. A pulsing device for determining recurrent timing intervals includinga voltage operated current switching device, first means to stabilizesaid device against ambient temperature variations, and second means tostabilize said device against voltage variations.

10. A pulse interval timing apparatus including an electronic dischargedevice having an input circuit and an output circuit, temperaturevariation compensating means included in said input circuit, and currentvariation compensating means included in said output circuit.

ll. A pulse switch generator of the gaseous relaxation type includingcircuit means to compensate for temperature and input power variations.

12. A pulse switch generator according to claim 11 wherein suchcompensating circuit means include resistance elements.

13. An electronic pulsing device comprising, in combination, a gas tubehaving at least a grid, an anode and a cathode, a source of operatingpotentials associated with said tube, a timing network includingresistance and capacitance means connected to the grid of said tube, theresistance means of said timing network compensating for temperaturevariations, and a pulse output circuit including resistance andcapacitance means connected to the cathode of said tube.

14. The pulsing device of claim 13 wherein the resistance means of saidoutput circuit compensates for variations of operating potentials.

Menkhaus Dec. 5, 1950 Nilles July 20, 1954

